On a stationary warewasher or dishwasher (e.g., a batch-type or box-type dishwasher), wash arms located on the top and/or bottom of the washing chamber wash wares located in a dish rack by directing a washing solution out of nozzles located on the arms. The sprayed washing solution is typically a recirculated solution that, once sprayed, falls and collects in a sump below the chamber, is drawn from the sump through a strainer by a pump and is pushed by the pump along a flow path into the wash arms and then out through the nozzles. One or more rotatable rinse arms may also be provided for spraying fresh rinse liquid. In a flow-through warewasher (e.g., a continuous-type warewasher), wares are moved through a chamber (e.g., via a conveyor that moves racks of wares or via a conveyor with flights that hold wares) with multiple spray zones (e.g., a pre-wash zone, a wash zone, a post-wash or pre-rinse zone and a final rinse zone, each having respective nozzles) as they are cleaned.
Regardless of machine type, chemicals may be added to the wash and/or rinse liquid sprays during ware cleaning operations to increase the effectiveness of the operation. For example, detergent, sanitizer, rinse aid and/or deliming chemicals may be used in the warewash machine at various times. The chemicals are typically pumped from a storage container (e.g., a bottle or tank) at desired stages and in desired amounts. On a commercial warewasher, it is sometimes required and always advantageous to inform the machine operator when it is required to add additional chemicals to the supply bottles or tanks. The results for the end user will be the best when the operator knows precisely when the chemicals need to be replenished, therefore accurate and responsive sensing of the chemicals is the goal. Also, making the sensor work for multiple chemical brands/formulas is desirable.